David Robson: Help those plants take root this winter

David Robson

Thursday

Sep 24, 2009 at 12:01 AMSep 24, 2009 at 7:48 AM

As the season ends, gardeners make every last ditch effort to keep plants for as long as possible. We’ll cover tender annuals with sheets and blankets and start shifting pots around, all in an attempt to prolong the inevitable.

The end of the gardening season is approaching, sometimes seemingly in a headlong rush toward the finish line, while other times it seems it’s dragging its feet set to come in last.

But it eventually will arrive. Make no mistake. Soon the leaves will drop en masse, the wind will start howling and white stuff will pile up on the ground.

As the season ends, gardeners make every last ditch effort to keep plants for as long as possible. We’ll cover tender annuals with sheets and blankets and start shifting pots around, all in an attempt to prolong the inevitable.

Some will bring pots of flowers and vegetables indoors, giving them as much light as possible. All looks well during October and November until the furnace starts drying out the air and we swell with pride at our fooling of Mother Nature. But like the old margarine commercial, you can’t fool her.

Bugs that hitchhiked indoors explode. Light intensities decrease enough that leaves start falling in large quantities. Often, plants are discarded to make room for holiday decorations, or with the holiday decorations in January.

Still others will rely on taking cuttings to bring a little of Summer 2009 indoors during the coming winter.

Cuttings hold several advantages over larger plants, one of which is that you don’t have as much guilt when they die. You’ve already pruned the plant and left it for the elements. If the offshoot doesn’t make it, it’s not a big deal.

Cuttings take up less space. Instead of a large unwieldy pot of geraniums, you have a cutting that takes up less than 10 square inches.

There’s also the adaptability issue.

Smaller plants, especially the newer growth that cuttings seem to encompass, can adjust to lower light intensities indoors as well as drier air. It doesn’t mean that they thrive with the less-than-ideal conditions, but they survive. Hopefully.

Not every plant responds well from cuttings. Many do, though, and many give surprisingly good results for most of the winter depending on how you root them.

First, the worst substance to root a cutting in is water. Sadly, the most common substance gardeners use is water.

It’s easy to see why water is so commonly used. Stick a cutting of coleus, one of the easiest plants to root and overwinter, in water, and in a matter of days, you’ll have roots filling the jar or glass. Replenish the jar with fresh water once a week, and the coleus goes to town. Soon you’ll have roots everywhere.

But try to transplant the cutting now. All the water roots dry up in the soil, and the cutting starts dying.

The same thing applies to impatiens, another common cutting. It doesn’t root as easily, but eventually, it will form roots. However, just looking at a teaspoon of soil causes the roots to shriek in fright and die.

There’s a big difference between water roots and soil-borne air roots.

Water roots receive little air even though there is some oxygen in the water. But if the water isn’t changed often, oxygen levels are depleted. Roots turn brown, and the plant wilts. Even if you change the water regularly, the roots rebel when planted in soil. Once completely surrounded by water, they are now covered with potting soil.

Now you have to contend with a soggy soil that may not have enough oxygen to support the old roots and too much water for the new roots that develop in the potting medium.

You really have two options for indoor success.

First, root cuttings in a loose medium such as sand, perlite or vermiculite. The latter two can be found at many garden centers, nurseries and home improvement stores. Sand can be picked up at most beaches.

Keep the loose medium moist, and you’ll still get roots. Maybe not as fast as on the kitchen window sill in the canning jar, but roots will form.

Since they are “soil” roots, there will be little to no transplant shock when cuttings are finally potted.

The other option is to root in water, and as soon as you see roots form, transplant the cutting to a loose potting soil and keep your fingers crossed that the plant will live.

There probably is a third: root the cuttings in water, enjoy them as long as possible, making sure to change the water often to keep it oxygenated, and when the cuttings die, toss them in the compost pile.

Give cuttings and rooted plants as much light as possible.

Besides coleus and impatiens, many begonias and geraniums will root on the kitchen windowsill. As a rule of thumb, the fleshier the stem, the easier it will root.

Take 4- to 6-inch cuttings from the end of the plants. This new growth tends to root faster and easier than older tissue.

Strip the bottom two inches of foliage and place the cut end into the rooting medium. Keep moist, but not soggy.

Bigger isn’t better. Larger cuttings may wilt before rooting or become impossible to transplant successfully after roots form. It’s better to make several smaller cuttings and combine the rooted plants together down the road.

Petunias, marigolds and zinnias won’t root well. Neither will basil, though some have had success.

Some of the tropicals will root, but you may be better off cutting the plants back severely, and allowing new growth to adapt to indoor light and humidity levels.

State Journal-Register contributor David Robson is a horticulture educator for the University of Illinois Extension. For more gardening information, go to www.extension.uiuc.edu/mg.

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